1. Field of the Invention
This invention pertains to a novel method for cleaning pipelines using aqueous, cross-linked gelled pigs.
2. Declaration of the Prior Art
Pipeline efficiency and volume can be lost by scale build up in the interior lining of the pipe. Mechanical pigs and/or gelled chemical pigs have been used to remove the scale. The mechanical pigs are normally solid bullet-shaped devices which have wire brushes or abrasive surfaces to physically abrade the scale interior of the pipe. The gelled chemical pigs, on the other hand, remove the surface deposits by dissolution and/or by picking up loose debris as they pass through the pipeline.
A new aqueous gelled pig containing bactericides was described in my patent application, Ser. No. 096,106. The gelled pigs described there are extremely effective in removing bacteria-containing scale from pipelines. As one example, a pipeline laden with sulfate-reducing bacteria was cleaned from the interior of a pipeline by passing through it a gelled pig whose composition comprised a borate cross-linked hydroxypropyl guar gum containing an organic quaternary ammonium salt as a bactericide. Some of these bactericide-containing gelled pigs are species of the generic invention described below.
A new method of drying pipelines was described in my patent application, Ser. No. 122,536. This method comprised sequentially passing through the line (a) an aqueous crosslinked gelled pig, (b) a fluid mobility buffer comprising a non-crosslinked gelled pig, (b) a fluid mobility buffer comprising a non-crosslinked gelled alkanol of from one to three carbon atoms, and (c) a dessicating amount of a liquid alkanol of from one to three carbon atoms. As an example, a pipeline was dried by sequentially passing through it (a) a borate crosslinked hydroxypropyl guar gelled pig, (b) a fluid mobility buffer comprising methanol thickened with hydroxypropylcellulose, and (c) methanol.